Rails 5—How to add UUID column

Question

There doesn't seem to be much documentation on UUIDs in Rails 5. All I've found is this code:

create_table :users, id: :uuid do |t|
  t.string :name
end

That works great if you're creating a table, but what if you're updating an already-existing table?

How do you add a UUID column to a table?

Answer 1

To migrate from default id to use uuid, try writing migration like this:

class ChangeProjectsPrimaryKey < ActiveRecord::Migration
   def change
     add_column :projects, :uuid, :uuid, default: "uuid_generate_v4()", null: false

     change_table :projects do |t|
       t.remove :id
       t.rename :uuid, :id
     end

     execute "ALTER TABLE projects ADD PRIMARY KEY (id);"
   end
 end